The Remarkable Results of the 1883 Eruption of Krakatau

Earth Observatory Blog

The Remarkable Results of the 1883 Eruption of Krakatau

Today marks the anniversary of the 26-27 August 1883 eruption of Krakatau Volcano, Indonesia

The 1883 eruption of Krakatau (also widely known as Krakatoa) volcano in Indonesia has captured the imagination of many people – from the first Malay account of the eruption by Muhammad Saleh (Syair Lampung Karam – published in Singapore) to the 1969 film Krakatoa, East of Java, starring Maximillian Schnell.

And how not? The eruption is remarkable in many ways. Early signs of unrest began in May 1883 and increased in intensity until the climactic eruption commenced on 26 August, with a large ash plume extending upwards of 27 kilometres (km) into the sky and the generation of a small tsunami.

From 5.30 am to 10.41 am (local time) on 27 August, the eruption culminated in four large explosions, each producing a tsunami. At 10.02 am, the largest explosion ever heard rang out from Krakatau to distances as far away as Alice Springs, Australia, and Rodrigues Island, Mauritius. It was certainly heard in Singapore.

An ash plume reached an estimated 80 km in altitude, darkening the sky for the rest of the day. Activity ceased abruptly at 11.00 pm and quiet returned. Yes, this eruption of Krakatau was remarkable indeed.

This eruption marked the beginning of a new scientific endeavour, the study of sound below human detection – also known as infrasound. Recall that the 10.02 am explosion was heard by people thousands of kilometres away from Krakatau. Although people in Berlin, Germany, and Washington D.C., U.S., could not hear the explosion, instruments (called barographs) also recorded its occurrence.

How did this happen? Sound “happens” when air molecules vibrate rapidly, which cause rapid changes in air pressure; the louder the sound, the larger the vibrations, and the larger the changes in air pressure. If sound is large enough (i.e. 194 decibels) the air pressure changes can reach zero. When this happens the sound will start to push the air, creating a shock wave. In this case, the sound can literally be deafening if you are too close. Sailors on the British ship Norham Castle,only 64 km from Krakatau, experienced the shock wave and as a result, their ear drums burst. As the sound and shock wave travel further from the volcano and around the world, the volume diminished but still air was pushed ahead. This is how barographs in Europe and North America recorded evidence of the eruption of Krakatau.

Since the eruption, infrasound studies have expanded and allowed scientists to study large infrasound-producing events globally, including meteorite impacts, volcanic explosions, and even the detonation of nuclear bombs. Here at the Earth Observatory of Singapore (EOS), Assistant Professor Benoit Taisne uses an infrasound network located in MacRitchie Reservoir Park to monitor explosive eruptions from Java and Sumatra in Indonesia. The Volcano Group at EOS is currently researching methods to use this information to aid in the early warning of large volcanic eruptions for the aviation community, due to the hazardous effects of volcanic ash on aircraft engines.

With help from telegraphic relays sent from Batavia (now known as Jakarta), Indonesia, the world learned of the eruption within 24 hours. The 1883 eruption is considered to be the first natural disaster to be reported that quickly. Today, thanks to Twitter and other social media outlets, we can learn about the most recent volcanic eruption or earthquake within minutes of its occurrence. EOS is active on Twitter (@EOS_SG) and Facebook (@EarthObservatoryOfSingapore) to share the latest news, announcements and analyses of our changing Earth.

To learn more about the 1883 Krakatau eruption, please check out the following: